The invention concerns a tool for connecting an end of a first pipeline to an end of a second pipeline supported by a subsea structure and being provided by at least two guide elements. Further, the invention also concerns a method for connecting the ends of first and second pipeline, wherein the second pipeline is supported by a subsea structure and being provided by at least two guide elements, and a tool comprising means for connecting the pipeline ends.
Subsea installations for oil and gas extraction are commonly connected together by pipes, commonly called pipeline (or flowline) spools. The connection may for example be between a well and a manifold, or flowline (having a T-junction), or between template systems. In this case a length of pipe (a spool) is made on the surface, in each case fabricated to fit the distance between the hubs provided at the end of the pipelines. A termination head is normally fitted to each end of the spool. There are two main methods for the installation of such spools. In vertical installation, so-called stab-and-hinge method, the spool is deployed vertically and fitted into a receiver on the installation. Thereafter the spool is rotated to a horizontal position and the first (hinge) end is connected up with the piping hub on the first installation (commonly called the inboard hub), and then the second end is connected. An example of this method is disclosed in NO Patent No. 319639.
In horizontal installation the spool is suspended from a carrier frame in a horizontally position and both ends are landed simultaneously in the receiving sections of the installations. Then the termination head is pulled towards the inboard hub and the connection is made up. See for example FIGS. 13 and 14 in PCT application WO 0179736.
Vertical installations can impose heavy loads on the seabed structures as they are landed and rotated. There is also a need for guiding structures to ensure correct alignment before the connection is made up.
WO 0179736 describes a horizontal connection where a support frame, or cradle, is coupled to each termination head. The cradle includes a collar that lands on the inboard hub. The termination head is now in the correct alignment for connection and can now be moved towards the inboard hub, by using an ROV tool. The disadvantage with this system is that it is complicated and that the whole weight of the spool will rest (through the collar) on the inboard hub.